Mechanical communication switchboard



March 31, 1953 w. w. CARPENTER EIAL 2,633,502

MECHANICAL COMMUNICATION SWITCHBOARD Filed April 26,1949 13Sheet-s-Sheet l .W W CARPENTLR #vvnvrons R 8. MURPHY ATTORNEY w. w.CARPENTER ETAL 2,633,502 MECHANICAL COMMUNICATION SWITCHBOARD March 31,1953 13 Sheets-Sheet 2 Filed April 26, 1949 FIG. 2

WW CARPENTER R VBLMURPHV a a. 6

lNl/E N TOPS AT TOR/VEV March 31, 1953 w. w. CARPENTER ETAL 2,633,502

MECHANICAL COMMUNICATION SWITCHBOARD Filed A rii 26, 1949 13Sheets-Sheet 3 INVENZOIRS ER ATTORNEY March 31', 1953 w. w. CARPENTERETAL 2,633,502

MECHANICAL COMMUNICATION SWITCHBOARD Filed April 26, 1949 13Sheets-Sheet 4 w WCARPENTER g? B. MURPHY AT TORNE V March 31, 1953 w. w.CARPENTER ETAL 633502 I MECHANICAL COMMUNICATION SWITCHBOARD Filed April26. 1949 1a Sheets-Sheet 5 W H. CARPE/VTfR P B. MURPHY 2/6 y f a 2/4ATTORNEY INVENTORS March 31, 1953 w. w. CARPENTER ETAL 2,633,502

MECHANICAL COMMUNICATION SWITCHBOARD Filed April 26 1949 13 SheetS-Sheet 6 INVENTORSR B. MURPHY ATTORNEY WW CARPENTER March 31, 1953 w. w.CARPENTER ETAL 2,633,502

MECHANICAL COMMUNICATION SWITCHBOARD Filed April 26, 1949 15Sheets-Sheet '7 Ill [la w WCARPENTER WVENTORS- P BI MURPHY ATTORNEY 4March 31, 1953 w. w. CARPENTER ETAL 2,633,502

MECHANICAL COMMUNICATION SWITCHBOARD Filed April 26, 1949 l3Sheets-Sheet 8 FIG. /7b

FIG. 16'

159- I60 F (G FIG FIG l9 l8 2/ 0 F 1 I66 A =9 I45 Ha. Ha. 'Q

FIG. 2a l/mrops W CARPENTER B P. B. MURPHY y M rina. CWj

ATTORNEY March 31, 1953 w. w. CARPENTER ETAL 2,633,502

MEbl-IANICAL COMMUNICATION SWITCHBOARD Filed April 26, 1949 isSheets-Sheet 9 712 n. CARPENTER INVENTORS' P. B. MURPHY AT TORNE Y R [Vv. 2 w w 0 P R s, Wm W m w w W 4 m 2 m s w. w. CARPENT ER EI'ALMECHANICAL COMMUNICATION SWITCHBOARD OTHER-CORD CIRCUITS March 31, 1953Filed April 26 1949 RING/N6 CIRCUIT March 31, 1953 w. w. CARPENTER EI'AL2,633,502

MECHANICAL COMMUNICATION SWITCHBOARD Filed April 26 1949 l3 Shee ts-Sheet ll OT/IER SUBSCRIBER C/RCUHIS' m v. W "w M we we INVENTORS a N m l AMatch 31, 1953 w. w; CARPENTER 1:111. 2,633,502

MECHANICAL COMMUNICATION SWITCHBOARD Filed April 26, 1949 13Sheets-Sheet 12 FIG. 2/

ATTORNEY March 31, 1953 w. w. CARPENTER EI'AL 2,633,502

MECHANICAL COMMUNICATION SWITCHBOARD Filed April 26, 1949 1sSheets-sheet 13 FIG 22 //vvE/vroRs @5553? BY z. e I

A T TORNEY Patented Mar. 31, 1953 UNITED STATES PATENT OFFICE MECHANICALCOMMUNICATION SWITCHBOARD Warren W. Carpenter, Garden City, and Paul E.Murphy, Grand View, N. Y., assignors to Bell Telephone Laboratories,

Incorporated, New

York, N. Y., a corporation of New York Application April 26, 1949,Serial No. 89,757

53 Claims. 1

The present invention relates to switching mechanism for establishingconnections between selected pairs of a plurality of communicationchannels.

In conventional automatic central office equiption of a connection. Onaccount of this complexity the automatic exchange compares unfavorablywith semi-automatic or manual exchanges, in addition to the fact thatthe automatic equipment is inferior to that of a manually operatedswitchboard as far as ruggedness and mechanical stability is concerned.

The general object of the present invention is to provide a novel typeof switching mechanism combining the ruggedness and simplicity of theordinary manual switchboard with the speed of operation and ease ofsupervision of an automatic exchange.

More specifically it is an object of this invention to provide, in acommunication system, an automatic switchboard operator or robot adaptedto put through to a selected subscriber or trunk a call originating witha calling subscriber or trunk, by establishing a plug-and-jackconnection between the two lines, and to break the connection physicallyupon reception of a supervisory signal, thereby restoring the mechanismto normal.

Another object of the invention is to provide, in a central ofiice orprivate branch exchange including switch means'individual to respectivelines and switching equipment common to a plurality of lines, a noveltype of mechanism for automatically establishing a connection betweentwo lines in such manner that no part of the common equipment remainsengaged once the connection has been set up, communication beingmaintained by means of a pair of cord-connected plugs and associatedcircuits of which enough are provided to take care of anticipated peakloads with a minimum of delay.

A further object of this invention is to provide a robot mechanism ofthe character described having means for automatically insertinganswering plugs and calling plugs into jacks and for withdrawing theplugs at the end of the conversation, and for gathering up unused plugsin such manner as to keep them in preparatio to answer an incoming call.

Still another object of the invention is to provide, in a communicationsystem, simple and effective means for automatically inserting a maleconnector or plug into a selected one of a plurality of femaleconnectors or jacks.

A still further object of this invention is to provide, in acommunication system, means for selectively disengaging idle plugs fromtheir respective jacks and for preventing jamming of the mechanism dueto entanglement of their assoclated cords.

' Broadly speaking, the invention provides, in combination, in acommunication system comprising a plurality of incoming and outgoingchannels, operating mechanism for picking up a plug associated with anincoming channel in response to a call signal received over saidchannel, a control circuit responsive to directionindicating signals,received over the incoming channel, for directing said mechanism toinsert the plug into a jack associated with a selected outgoing channel,and disconnect means responsive to a supervisory signal, received overone the supervisory circuit in such manner as to deposit a supply ofavailable answering plugs in a magazine whenever the respective cordcircuits are idle, then in response to a call signal to direct the plucarrier toward the jack associated with the calling line, operate theplug carrier to transfer one of the answering plugs from the magazine tothe said jack, cause the plug carrier to pick up the calling plug pairedwith the said answering plug, subsequently to direct the plug carriertor ward another jack in accordance with line selecting signals receivedover the calling line, operate the plug carrier to insert the callingplug into the selected jack, thereupon to return the plug carrier to anormal position in readiness for further calls, and finally to effectthe withdrawal of both plugs from their respective jacks in response toan end-of-connection signal. The plug 'carrier is arranged to carry outtwo different movements, preferably in horizontal and in verticaldirection.

The robot mechanism may be used to effect connections between subscriberlines, between trunk lines, or between trunk and subscriber lines, andis applicable to central ofices as Well as to private branch exchanges.The number of lines served by each robot mechanism may be a multiple ofthe number I of cord circuits provided therein, the ratio generallydepending on the number of connections which the equipment is designedto handle simultaneously at peak load.

Where the load is particularly heavyand the number of lines served islarge, two or more robots according to the invention may be arranged'intandem, with the lines multiplied thereto, for .the purpose of givingincreased traffic-handling facilities without undue mechanicalcomplications of the equipment. In such an event it will also bepossible, through the use of control switches ofa type known per se, todesignate one or more robots as the principal switching equipment andto' use one or more other robotsas a spare or spares, to baconnected incircuit only when a principal .robot becomes electrically.ormechanically .dis ahled.

The above and other objects and features of'the invention will, becomemore fully apparent from .the followingdetailed' description; referencebeing had tothe accompanying drawings in which:

:Flg. l'is atop plan view of a switching apparatus according to theinvention;

"Fig.2 is a -front view. of the apparatus shown in Fi 1;

Fig.- B'isa view insectional elevation taken at right angles to that ofFig. 2 and showing the principal parts of the apparatus in side view;

Fig.1.- -isa :fragmentary top view. on a larger scale-than the precedingviews, with parts broken away to: expose the underlying elements: of theapparatus;

5 isa fragmentary front elevation of the plug carrier. and adjoiningparts of the apparatus; "Fig: 6 is a sectional view taken on the line6+5 ofliig; 5;

Fig.- 7 shows, in front view, certain switches controliingthe movementofthe plug carrier;

Fig; 8 is asectional view taken on the line 8-8 ofFig; 'i;

9 is'a top plan View of the; cord pulling mechanism used'for breakingdown connections;

E'Fig. 'lllfis an elevational section" taken on the line 1 6'l 9 of Fig.9;

Fig. 111s an. illustration of. a detail of.:the cord pulling :mechanism,taken :on the line 1 1-1 i' of Fig; 10;

:4 Fig..12tis a vieucin side elevation of the pick-up mechanism used fordeliveringplugs to theiplug :carrier;

EFig. v131s a fragmentarytopview of'the pick-up 'mechanism,takenion theline 93-13 of Fig.12;

I Fig. 14 is a rearview of the magazine portion of the" plugcarriery'taken on the line i4.|4 of Fig. 15 is a sectional elevationofthe plug carrier, :showing the plug transfer mechanism thereof;

Fig; 16 is a fragmentary front view of the plug carrier;

.Fig. '17 is a sectional view taken on the line fl- -l'l of Fig. 15;

Figs. 17a, 17b, and 170 are views similar to Fig. 17 but showing theplug transfer mechanism in 'diiferent operating positions;

18 is a circuit diagram of the apparatus proper, showing the variouselements thereofin approximately'the relative position they occupy inFigs. 1 (top of Fig. 18) and 2 (bottom of Fig. 18);

4. Fig. 19 is a circuit diagram showing a plurality of cord circuitsassociated with the apparatus;

Fig. 2G is a circuit diagram showing a plurality of subscriber linecircuits associated with the apparatus;

Figs; 21:. and "22 show different parts of the supervisory circuitassociated with the apparatus;

and

Fig. 23 shows the relative position which Figs.

. l8. through22 occupy in the overall circuit diagram.

Introduction -Two subscriber-line circuits and one cord circuit areshown in complete detail by way of example. Only a small number ofcords, jacks and selected by the calling subscriber.

plugs have been shown in the various views, in their proper places, forthe sake of clarity. Conventionalpperating devices such as levers, gearsand chains shown otherwise in the various structuralyiews, have beenindicated by dot-deshlines inthe .circuit diagrams.

.The only part oflthe, system not. shown. and described in detail is aselector circuit provided for. the purpose of marking the. jack. of .aline This circuitis fully conventional and responds todirectionindicating signals, such as dial pulses, sent over the. callingline.

, The apparatusillustrated in the drawing has been designed forcnethousand subscriber lines served by forty cord circuits. The associatedjacks are. distributed over twenty jack plates each carrying. fiftyjacks. The unit actually con:- structedhas a width of 32,, aheight of43", and a depth of 34". It will be understood that. these figures aregiven merely as. an illustration and in no way limit .the invention.

General construction X as. 3)

."The various .parts or the robot; mechanism about to beldescribed aresupported on a frame! which comprises a base 2, cross bars 3; 4* andfour uprights 5, 6, l and 8. Two pairs'of connecting pieces 9; is andii, 12 span the uprights 5, l and 8 respectively; cross bar 3 beingsuspended from piecesfi, ii and cross bar t being similarly "suspendedfrom pieces ill, 12. The base 2 rests on additional: crcsspieces I3, Hiwhich also support ta rear plate 5 of generally segmental configura-1011.

Rising vertically from the base 2 area plurality ofispaced' paralleljack'plates' Hi each mounting a row of vertically spaced jacks i? oneach face thereof; together with a like number of pairs of commutatorsegments iSA, l3C for answering and calling, respectively. Displaceablein front of these jack plates isa horizontally movable carriagele'supporting a plug carrier 29 iorvertical travel. The carriage ll'isprovided with an upper grooved roller 2 engaging a vertical guide rail22 depending from the cross bar 3, and with a lower grooved roller'2-.;engaging a similar rail 24 rising from-the base 2. Other rollers 25, 25engage horizontal guide rails 2?, 28 supported on cross bar 3 and onbase 2, respectively. Each pair of adjacent jack plates H3 definesavertical channel in which the plug carrier 25? may move up and down onthe carriage ill.

The plug carrier Zliengages the verticalmembers or legs 28, 3B of thecarriage l9 and is connected through coil springs 3 l, 32 to the extremities of a steel ribbon 33 which passes under tensioniaroundan'upper pulley 34 and a lower pulley 35. The latter pulley is drivenvia gears 36, 31 and 38 from an elongated pinion represented by agrooved rod 39, this rod in turn deriving its motion from the shaft of amotor 49 controlling the vertical travel of the plug carrier. (Thisarrangement is shown more clearly in Fig. 4.) The leg 30 of the carriagmounts a pair of vertically spaced bearings 4|, 42 in which there isjournaled a rod 43; a serrated strip 44, resiliently suspended bysuitable means (not shown), is secured to this rod by means of studs 45,engaging slots 45, thus allowing for a certain play in the verticaldirection. Strip 44 has a magnet armature 41 secured thereto and maypivot on rod 43 under the control of a vertical stop magnet 48; whenthis magnet is energized, one of the saw teeth on strip 44 cooperateswith a lug 49, provided on the plug carrier 20, to arrest the latter ina position aligned with a desired jack I1.

Horizontal movement of the carriage I9 and, with it, of the plug carrier20 is controlled from a motor 50 driving a pulley this motor beinglocated on the right-hand side of the apparatus as viewed in Fig. 2. Asimilar pulley 52 is mounted on the left-hand side, the two pulleys 5I,52 being engaged by a steel ribbon 53 connected under tension, throughcoil springs 54, 55, to the legs 29, 30 of the carriage i9. In order toinsure parallel movement of the upper and the lower end of carriage l9,the latter is provided with a vertical shaft 56 carrying a lower pinion51 and an upper pinion 58, meshing respectively with a rack 59 supportedon base 2 and with a rack I30 supported on cross bar 3.

The upper portion of the carriage I9 and adjoining parts of thestructure are more clearly shown in Figs. 5 and 6.

The principal functions of the apparatus, apart from the displacement ofthe plug carrier, are carried out by six motors designated GI through66. Three arms 31, 68 and 59, all swingable about a common pivot locatedcentrally at the cross bar 4, are operated by these motors in a mannersubsequently described to pick up answering plugs, pick up calling plugsand withdraw answering as well as calling plugs, respectively.

The plugs generally designated 1!, have cords 12 connected thereto andare grouped into answering plugs HA and calling plugs 'EIC. As viewed inFig. 1, the right-hand side of the ap-- paratus is reserved foranswering plugs and cords, the left-hand side being reserved for callingplugs and cords.

Individual compartments 13A, 136 for each answering and calling cord areformed in the, rear of the machine by a plurality of partitions 14,rising from the rear plate I5 and extending radially toward the pivot19, these partitions being provided with inner flanges 75 and outerflanges 16 forming front and rear walls for the respective compartments.They also carry socket pieces 11 adapted to receive idle plugs 1 L4 orNO, this being more clearly shown in Fig. 12. There are further providedin each compartment 3, pair of guide rollers 19, 19 for guiding thecords 12 during movement of their plugs. Other, vertical guides 89 aredisposed at'intervals to fa-' cilitate movement of the plugs and prevententanglement of the cords.

The sweep of the arms 61, 68 and 39 is determined by three pairs oflimit switches SI, 82; 83, 84; and 85, 86. Switches 3!, 82 mark the endsof an answering-plug pick-up track 81, associated with arm I51; switches83, 84 mark the ends of a respective compartments 13A, as well as asolenoid 92 provided with a plunger designed to drop intoone of severalholes 93 in order to align the arm with a selected answering plug 13A.In like manner, the arm 08 carries a contact spring 94, cooperating withcontacts 95, as well as a solenoid 96 adapted to engage any one of anumber of holes 91 on track 38. Arm 69 is provided with a contact spring98, arranged to engage contacts 99, and with a solenoid I99 the plungerof which may enter any one of a plurality of cutouts I0! formed on thetrack 89.

Arm 6? is designed to pick up answering plugs TIA and deposit them in achamber of a stationary plug magazine. Arm B3 is similarly designed topick up calling plugs H0 and deposit them in another chamber of the plugmagazine. Arm 69 is designed to engage the cord 12 of any plug 1| nolonger in circuit for the purpose of withdrawing the plug from the jackI1 into which it had been inserted by the plug carrier, thereby makingboth the jack and the plug available for further calls. Beforeproceeding with the description of the operating mechanism associatedwith each of these arms, it will be desirable to describe in some detailboth the plug carrier and the magazine.

The plug magazine (Fig. 14) This element, generally indicated at I02(see Fig. 14), is fixed to the rear of cross bar 3 in alignment with thecentral one of the vertical channels separating the jack plates I6 (Fig.2). The magazine I92 comprises a first chamber I03.

at the left in Fig. 14, and a second chamber I04.

Chamber I03 receives answering plugs 1IA from the arm 61 while chamberI04 receives calling plugs 1IC from the arm 63. The two sides of themagazine I02 are identical, except that the left-hand side is providedwith a pair of contacts I05 which are closed when the chamber I93 isless than full. Contacts I05 and I01, at the bottom of the magazine, areclosed when a plug is in chamber I03 or I04, respectively.

Associated with the two chambers are a pair of solenoids I08, I09. Eachsolenoid operates a pair of bell crank levers Ill], III (see also Fig.12) adapted to push an answering plug or a calling plug into the plugcarrier 20 when the latter is in its home position adjacent the magazineI 92, this being also the position in which the plug carrier is shown inFig. 2. The plungers of the solenoids also operate switch-over contactsII2. I I 3. respectively, for purposes subsequently described. I Tofacilitate the work of the pick-up arms 51, 5B, the magazine is providedwith two wings II4, ll 5 extending at a slight incline from the top ofthe chambers I03, Hi4, respectively, thus forming chutes over Which theplugs may slide into'these chambers. This action is assisted by a pairof fingers H6, II! which are adapted to oscillate in slots H8, H9,provided in the wings H4; H5,

underthe control. or anauxiliary motorl' 112E supported from the crossbar 3. The two fingers are interconnected by a link:v IZt which isreciprocatedby means of a lever I22 connectedto a crank 23; thelatter'being rotated from the motor l2il through the intermediary of gears.1'24 and I25. Motor IN is connected to. be energized simultaneously withthe pick-up devices associated with arms 67, 58.

The plug carrier (Figs. 4, l5, 16, 17)

The principal parts of this unit are a casing 25, a pair of plug holdersi217, I28 inside the casing, a plug transfer mechanism generallyindicated at I28, and a plug connector motor I38 carried outside thecasing I25.

Each of the plug holders comprises an upper and a lower jaw, the lowerjaw being fixed to a portion of the casing, the upper jaw beingyieldably mounted on fiat spring arms I35, I32, re epectively, securedto the casing through a'single insulator iSS, which may be of hardrubber, in the case of arm 33 I and a pair of similar insulators I34,lid in the case or arm I32. Each of the spring arms I3I, M2 is providedwith 2. lug I35, I31 which, passing through an aperture I33, I39 in thecover IE6 or the casing, prevents the jaws from closing without,however, interfering with the upward displacement of the upper jaw. Intothese holders the plug II is inserted sideways, through the action ofhell crank levers I to or 1H (Fig. 14), to be dislodged in likemanner-by the mechanism I29 for transfer to an adjacent jack II.

The transfer mechanism comprises a shaft I tf which is journaled in abearing MI and extends into the center bore of a sleeve member 442,being entrained by the latter through a pin I43 which engages a slot I44provided in the sleeve member M2. A spring m urges the member M2 towardsthe front wall of the casing I26 through which the reduced-end of thismember-projects, carrying a gear Mtwhich meshes with a pinion I51 drivenfrom the motor I39.

' Keyed to the free end of shaft hill is a crank arm I43 having a crankpin M5 which projects through the body of a pusher member I 59 havingprongs I'Ei, $52 and 'a stem I53. This stem passes slidably throughasleeve I5 l which itself is pivotally lodged. in bearings I55, I56. .Theprongs Ifii, I52 are of such length as to. clear a plug 'iI, held bythe. plug holders i2l, lZB. when the crank pin lie is in itsbottomposition shown in Figs. 15. and 17 the. casing. I26 is providedwith a pair of lateral cutouts I57, I58. through which the plug maybeinserted into. the holders, in the manner previously set forth, whenthe pusher'member I59 is out of the way. To transfer a plug from theholders #27, P intoa waiting jack i! (Fig. 170), each of the prongs 15!,I52 describes a noncircular path which brings the tip of the prong intoalignment with the plug and eventually causes the latter to leave the.holders I21, I28 and to enter the corresponding clips. of the jack. Thisis clearly seen in Figs. 17, 17a, 17b and 170 in which it. is assumedthat motor I38 rotates in such direction as to effect clockwise.rotation of the crank pin I48, as viewed in these figures. Fig. 17.shows the pushermember at rest; Fig. 170 illustrates the preparatoryswing of this member to the left; Fig. 17b shows the dislodgment of theplu II from the holder, an action which cams the upper jaw I2I' upwardsand away from that lower 3 aw l2I":to;free the phleiin' Fig. 17c,-finally,;.the plug has been inserted between theclips of. the jack whichwillsecurely retainit after the member 159 has completed its movementandroturned to its normal position.

The gear. I46 carries on its front face a pin I59 designed to cooperatewith a cam I56. which is formed on a depending portion of fiat springarm IBI, the latter being mounted on theinsulator I35. Arm I6I coactswith a projection; 162, depending from a. contact spring I63. to operatea set of contacts mounted in anqinsulating spring nest I64. Normally,the. arm IE! and the camrI-6II are in the position illustrated in. Fig.15 audiodicated in dot-dash lines in Fig..18; spring I63 then engageswith its lower contact. After. the pin I52 has made one. revolution. tothe. left or to. the right in Fig. 16, the assembly 160-153 is cammedupwards as shown in fulllinesinJ-Fig. 16 to open the lower contact andclose theupper contact of spring 53; this action .derenergizes motor I30(at the lower contacts) and shortcircuits .its armature (at the uppercontacts). thereby dynamically braking the motor.

. For the purpose of restoring the assembly to normal there is provideda'yoke I 55 the two. arms of which are formed with punched-outprojections I66, I61 adapted to engage the faceof gear. M5 well outsidethe. path of pin- I59. The lower ends of the yoke are hingedly securedto the. casing :25 by means of flexible straps 1358 permitting-aswinging movement ofthe yoke. The latter is provided at the top with aninclined portion I69 adapted to cooperate with a cam surface I'Ifl, de-

pending from the cross bar 3, for thepurpose oi tilting the yoke IE5.towards the left. (as viewed in Fig. 15) when the plugv carrier reachesitshome position adjacent the magazine I92. v.Suoha movement of. theyoke displacesthe toothed adisc M6 towards the left, against the forceof spring I 15, thereby disengaging the cam 60 from the pin 55% andpermitting the assembly fill-453- to return to normal, preparatory tothe next onersizaticn of motor I33.

Turning now more particularly to Fig/Lit can be seen there that the plugcarrier 29 is provided at its rear with a pair of hooks. Ill, I12adapted to engage respective angle pieces. H3, I'M provided. on the,left-hand and right-hand faces of jack, plates 56. Theseanglepiecesserve as guides for theplug carrier, angle piece H3 beingengaged by hook I72 when the plug carrier is positioned to. cooperatewithoneoi. theleithand jacks, angle piece I'M being engaged .by hookI'II when the. plug carrier is positioned to cooperate with one of therightrhand jacks. The angle pieces also serve to take up the reactionwhen the pusher member I53 transfers a. plug to a jack.

The plug carrier 29 is further provided with three pairs of guiderollers I75, I75, Ill, H8. I79, I; as best shown in Fig. 5, theserollers respectively engage the legs 28, 38 of the carriage. l9. Inaddition it carries two pairs of grounded springs IBIA, IBIC (Fig. 3),one pair on each side, for. the purpose of making contact withtheanswering and calling segments I 8A, IEC, respectively, which areassociated with the jack next to which the plug carrier is. to be.arrested.

Fig. 4 also shows the tip and ring connectors i323, 83 associated witheach iack II, as well as the tip, ring and sleeve terminals IM, and iSfithereof. Each jack plate I5 further carries a rounded deflector Iil'I.designed to guide the cord 2.

Fig. 4 makes it plain that the plug carrier has two positions in each ofthe channels which separate adjacent jack plates I6; 3, first positionadjacent the left-hand jacks of the right-hand plate, and a secondposition adjacent the righthand jacks of the left-hand plate. For thepurpose of marking a selected channel there are provided a plurality ofcommutator segments I88, carried on a commutator strip I89 which issupported on the base 2, these segments being engageable by a groundedbrush I99 mounted on the carriage I9 (see also Figs. 2 and 3). Thealternative stopping positions of the carriage within each channel areselected by an arrangement which is similar to the vertical stoppingmechanism 44-49, described in connection with Figs. 2 and 3, and whichwill be explained in connection with Figs. 5 and 6.

Horizontal stopping mechanism (Figs. 5 and 6) Two pairs of magnets I9I,I92 are mounted on the cross bar 5, each pair having an armature I93,I94 secured to one of the flanges I95, I95",

respectively, of a U-shaped channel member I95;

the latter is fixed to a bar I95 pivotally held in bearings I97, I99, aspring I99 (Fig. 2) serving normally to maintain the channel member I95in a neutral position shown in Fig. 6. The flanges I95, I95" areprovided with spaced-apart notches 299, 299", respectively, thesenotches cooperating with a pair of lugs 29!, 29I, respectively, when themember I95 is tilted counterclockwise or clockwise (as viewed in Fig. 6)by the energization of magnets I92 or I9I, respectively. The lugs 29I,29I are secured to the upper end of carriage i9.

* From Fig. 5 it will be noted that when the operation of magnets I92places a notch 299" in the path of lug 29 I the carriage will be stoppedin a position somewhat more to the left than if magnets I9I hadoperated, placing a notch 209" in the path of lug 29I. This arrangementpermits a relatively wide spacing of the notches on each of the tiltingmembers I95 and I95, thus making the time of energization of the magnetsless critical than if only a single tilting bar were used. Theinclination of the notches 290', 299" is reversed on opposite sides ofthe center channel without, however, changing their relative position(see also Fig. 7)

Home spring assembly (Figs. 7 and 8) Mounted on the cross bar 3 is aguide member 292 slidably supporting an actuating member 299 forverticalmovement. Cross bar 3 also supports a pair of spring nests 294and 205; spring .nest 294 comprises a spring 296 having upper and lowercontacts, while spring nest 295 comprises three springs 297, 298 and299, each associated with a single pair of contacts. Actuating member293 carries a stud 2H} adapted to engage the .mechanicallyinterconnected springs 201, 298-and i 299 when the actuating member israised, thereby closing all the contacts of nest 295; this member alsocarries a stud 2H for depressing the spring "296 when the actuatingmember is lowered, thereby causing spring 296 to open its upper con-.tacts and to close its lower contacts.

The plug carrier 20 mounts a contact roller 10 actuator to the positionillustrated in Figs. 7 and 8 is due to its own weight after the plugcarrier has descended.

The roller 2I2 also cooperates with a pair of contact bars 2I3, 2I4positioned to the left and to the right of the center channel,respectively. These contact bars are supported by brackets 2 I5, 2I9,depending from cross bar 3, for limited vertioal movement and arearranged toclose respective contacts 2 I '1 when engaged by the roller2I2. Bars 2I3 and 2I4 stop the upward movement of the plug carrier whenreturning from delivery of a plug to a jack.

Pick-up mechanism (Figs, 12 and 13) The two pick-up arms 5! and 68 beingidentical, only one of them- (the arm 68 delivering calling plugs to themagazine chamber I94) will be described in detail.

Motor 62 controls the swinging movement of the arm 99 through theintermediary of gears 2I8, 219, 229, 22I and sector gear 222. Motor 54,which is mounted on a bracket 229 (see also Fig. 2), rotates a sprocket224 which, together with a companion sprocket 225 disposed on the lowerend of the arm, supports an endless chain 226. This chain carries on itsouter periphery a hook 22'! the split end of which is adapted to engagethe forward part of a plug ll, while the same is held in the socket I1,and to carry the plug upwards towards the magazine I92, as indicated indot-dash lines in Fig. 12. The hook 221 is pivotally mounted and isprovided with vears 229, 229 which cooperate with a guide channel 239 toinsure the correct positioning of the hook,'so as to cause the same togrip the plug 'II near the bottom of its travel and to release the plugabove the wing i 45 of the magazine, thereby enabling the oscillatingfinger II? to deposit the plug in the chamber I94 thereof.

Fig. 12 also shows the contact spring 94, engaging contacts 95 on track88, and the solenoid 96 associated with the arm 58, as well as a guideroller 23I.

Pull-down mechanism (Figs. 9-11 The arm 69 is rotated from the motor 65(Fig. 1) over a train of gears 232, 234 and 235. Gear 235 is rigid witha lever 236 which pivotally supcarrying the gear 245, is journaled in ahousing 249 forming the lower part of the arm 59.. Gear 246 is mountedon a shaft 255 which also carries a rubber-tired wheel 251 and isjournaled in a diamond-shaped plate 252; the full lines in Fig. 10 showthe wheel 25! in idle position while the dot-dash lines indicate theoperated positionof the wheel and of plate 25I, the latter beingswingable about the shaft 248.

The shaft 259 further has mounted thereon a friction disc 2'55 designedto oppose to a certain extent the rotation of this shaft;this-arrangement prevents idle rotation of wheel 25I and causes theentire assembly 249, 259-253 to swing bodily forwards (counter-clockwisein Fig. when the motor 66 operates to rotate the gears in the directionindicated by the. arrows; conversely, opposite rotation of the motorwill cause the assembly to swing backwards (clockwise in Fig. 10) untilthe plate 252 encounters a suitable stop (not shown). The first of thesemovements forces the rubber-tired wheel 25! firmly against the cord 12of a plug to be withdrawn from its jack, thus clamping the cord betweenthe wheel and the guide roller it and resulting in the frictionalentrainment of the cord by wheel 256. The second movement disengages thewheel 25! from the cord after the associated plug has been received inits socket T. (Fig. 12)

It will be understood that the arrangement just described has thefurther advantage of adapting the friction between the wheel 25! and thecord to the amount of traction necessary for withdrawing the cord, sinceany increase in resistance will impede the rotation of the wheel,thereby tending to continue the forward swing of plate 252. If, however,the jamming of a plug or other unusual circumstances result in aninordinarily high resistance to pull, a safety device insertedbetweenthe motor 63 and the shaft 238 comes into play to prevent furtherstrain upon the cord by its engagement with the wheel 25L This safetydevice comprises two frictionally coupled clutch halves 254, 265 havingcontacts arranged to close when an unusually large torque displacesthese halves from their normal relative position, these contacts in turnreversing the rotation of motor 65 so as to disengage the wheel 25! fromthe cord 12.

Figs. 9 and 10 also show the solenoid we, associated with arm 59, aswell as the contact spring 98, engaging the contacts 89 on track 89, anda guide roller 256.

Brief description of operation When the plug carrier 20 is in itsnormalpcsition, reception of a call energizes the solenoid lii8-(Fig.14) to push an answering plug 1 IA from the chamber 33 of magazine H32into the holders I27, I28 of the carrier. Vertical motor as thenoperates to lower-the plug carrier from its home position to a positionjust above the jack plates 16, whereupon the horizontal motor 58displaces the carriage is to the left or to the right until the plugcarrier is aligned with the jack field in which an answering segment [8Amarked by the incoming call-is situated. The latter operation iscontrolled by the brush use, which detects a marked segment 188 on thehorizontal commutator strip 189, as well as by the stop magnets 19!, 192which operate selectively to arrest the carriage in one 'of its twoalternative positions associated with the selected vertical channel.Next the motor 46 moves the plug carrier down inside the channel untilits brush i8 IA contacts the marked segment iSA,'whereupon the plugconnector motor i 39 operates to insert answering plug 7 IA into theadjacent jack ii.

noid me then operatestoinsert the calling plug into the holders I27, I23of theplug carrier.

Motors iii and 5t thereupon direct theplug carrier toward the jack whosecalling segment 18C is marked by dialing pulses from the callingsubscriber. The calling plug is inserted and the plug carrier returnedto home position in readiness for further calls.

With the magazine chamber I03 less than full, motor 6i oscillates thearm 61 over the .track S1 to locate idle answering plugs, theirpositions being marked by ground on the associatedcontests 91. Motor $3functions to pick up the answering plug and deposit it in the magazinechamber its until the latter is .sufiicientlyfilled up to cause contacts25 to open..

When any plug inserted in a jackhas become idle by the breaking of theconnection between the calling and the called subscriber, the contact soassociated with the socket ii of this particular plug is marked andmotor M5 displaces the arm 69 over the track BQ toward-the empty socket.After the arm has arrived there, the retract-lug mechanism 25:, 252goes. into action under the control of motor 66 to impart traction tothe cord 72 connected to the respective plug, thereby withdrawing thelatter from its jack. Should such a withdrawal be prevented owing tosome mechanical interference, safety device .254, 255 disengages thewheel 25I from the cord and the arm (it moves onward .to thepositionofthe next plug marked for withdrawal. In this manher it will bepossible to have the arm 89 test the cords as to the relative case oftheir .withdrawal, and to prevent their entanglement by first effectingthe restoration of the readily retractable cords and only thereafterreturningto the cords that had to .be skipped during any swing of thearm.

Circuit description (Figs. 18-23) In Fig. 18 the motors, contacts andsolenoids referred to in the above description have been illustratedschematically and identified by the same reference numerals as used inthe preceding figures. Two answering plugs HA, HA, with cords 12A,721%.", have been shown by way of example, the associated contacts onthe tracks 87 and 89 being designated 9!, 9i" and 98A. 99A",respectively. Paired with these answering plugs are two calling plugsHC', 'HC" with cords 72C, 72C", respectively, the associated contacts onthe tracks 88' and 89 being designated 95, and 99C, 99C".

The diagram shown in Figs. 18-22 hasbeen simplified to the extent thatall auxiliary circuits for signaling, making busy tests and so forthhave been omit-ted; while such circuits will be providedin practice,they may be completely conventional and any detailed explanation oftheir operation is unnecessary for. an understanding of the invention.

Fig. 18 also shows connections to two jacks H, H" havingtip and ringconnectors I82 and 182" and I83, I83". The associated answering andcalling segments, designated I8A, 18C inFig. 3, have been combinedin'eachfcase to .a single segment l8, l8"; similarly; the'two pairs ofgrounded brushes I8IA, IBIC provided on the plug carrier have beencombined to two single brushes IN, 18!". This-simplification'has beenmade possible by the elimination of the auxiliary circuits referred toand has been'adopted for. the sake of greater clarity.

. Each cordlz comprises; tip, ring.tand sleeve visory circuit, alsoshows relays 304-315. remainder of this circuit, shown in Fig. 22,comconductors respectively indicated by numerals 251, 258, 259 followedby the designation of the cord, e. g. 251A. The tip, ring, sleeve andsegment conductors of the jacks 11' and 11" are indicated at 288', 261,262', 263' and 260", 261", 262", and 263", respectively. Associated witheach contact 91, on track 81, is a contact spring 264 which makescontact with the sleeve of a respective answering plug when the latteris retracted into its socket, as illustrated for spring 264 and plug11A. Similarly there is associated with each contact 95, on track 88, acontact spring 265 which makes contact with the sleeve of a respectivecalling plug while the latter is in the socket, as illustrated for plugs11C, 11C and springs 265', 265", respectively. Springs 264 arepermanently connected to their associated contacts while springs 265 arenot.

Fig. 18 also shows contacts 266 which are closed when the couplinghalves 254, 255 are displaced from normal relative position, and furthershows normally closed contacts 261, carried on arm 61, and 268, carriedon arm 68. These contacts are temporarily opened by cams 269, 210carried on the respective sprocket chains 226', 226" of these arms.

The contacts operated by the horizontal bars 213, 214, designated 211 inthe preceding figures, have been indicated at 211' for the right-handbar 214 and at 211" for the left-hand bar 213. Only two horizontalcommutator segments, 188', and 188", have been shown in Fig. 18, inaddition to a further segment 211 which marks the center channel.

The cord circuit interconnecting the cords 12A and 120' is shown indetail in Fig. 19. It comprises a number of relays 212-281 the functionof which will be subsequently described. Common to all the cord circuitsare five conductors 282, 283, 284, 285 and 286. Conductors 282, 283, 284lead to a machine ringing circuit 281 while conductors 285, 286 lead toa selector circuit 288 shown diagrammatically in Fig. 20.

Fig. 20 shows two subscriber stations 289, 289" and the line circuits290', 290" associated therewith. Each subscriber station is connected toits line circuit via line wires 291', 292 and 291", 292". The linecircuit comprises three relays 293', 294', 295 and 293", 294", 295",respectively. Leads 296', 296" extend from the line circuits to theselector 288, the selector being adapted, in response to digitalimpulses received from a calling subscriber, to apply a markingpotential (ground) to a selected lead 296.

Five conductors 291, 296, 299, 308 and 301 are common to all linecircuits 290. Leads 302 are common to some of the line circuits, therebeing one such lead for all subscriber lines associated with the jacksof a single jack field. Leads 302' and 382" are connected in thecircuits 290' and 298", respectively.

Fig. 21 shows a group of relays 383 each connected between battery and arespective lead 302. This figure, which represents part of the super-The prises relays 316-321 and 388, a stepping switch 328 having banks328a, 328b, and 3280, a stepping magnet 329 for this switch, and arelease magnet The conduc- ,t eee t p ati 9 t se 93 9 692. 6

supervisory circuit in Fig. 21. Conductors 331'. 331" terminate atcontacts 91, 91" on track 81; conductors 332', 332" terminate atcontacts 99A, 89A" on track 89; conductors 334, 334" lead to springs265', 265"; conductors 335, 335" terminate at contacts 95" on track 88;conductors 336', 336" terminate at contacts 99C, 990" on track 89.

The motor leads extending to the supervisory circuit are 338, 339 formotor 6|; 348, 341 for motor 62; 342, 343 for motor 65; the solenoids92, 96, 108 are also connected across these leads, respectively, inparallel with the armatures of their associated motors. Further motorleads are 344 for motors 63, 345 for motor 64; 346, 341 for motor 66;348 for the auxiliary motor 120, 349, 358 for plug connector motor 351,352-for vertical motor 40; and 353, 354 for horizontal motor 50.

Leads 355, 356 and 351 terminate at the brushes 88, 94 and 98,respectively. Conductors 358, 359, 368, 361 and 362, 363 extend from thelimit switches 81-86, respectively. Each of the contacts 255, 261, 268has a grounded lead and a lead extending to the supervisory circuit, thelatter lead being indicated at 364, 365, 366, respectively.

Other leads extending from the apparatus of Fig. 18 to the supervisorycircuit include a conductor 361 leading to the front contact of spring281; a conductor 368, leading to the stop right magnet 191, a conductor369 leading to the stop left magnet 192, and a conductor 310 common toboth magnets; a pair of conductors 311, 312 connected to the front andback contacts of the solenoid-operated switch 112, and a similar pair ofconductors 313, 314 connected to the front and back contacts of thecompanion switch 1 13; two conductors 315, 316 connected to the back andfront contacts of spring 286; a conductor 311 extending from themagazine contacts a conductor 318 extending from the vertical stopmagnet 48; leads 319', 319", terminating at segments 188', 188",respectively. A lead 388 terminating at the center segment 211; andconductors 381, 382 leading to the solenoids 188, 109, respectively.

Five additional conductors lead from the portion of the supervisorycircuit shown in Fig. 21 to that shown in Fig. 22. They are a conductor383, connected to .armaturesof all 383- relays in parallel; a conductor384, connected to the front contacts of the left-hand 383 relays; aconductor 385, connected to the front contacts of the righthand 303relays; a conductor 386, connected to other front contacts of all 383relays in parallel; and a conductor 381, connected to armatures of therelays 314, 315 in parallel.

It will also be noted that front contacts of the even-numbered relays883, such as 383", are connected in parallel to conductor 369 whilefront contacts of the odd-numbered relays 383, such as 383', areconnected in parallel to conductor 368.

In Fig. 22 the winding of relay 316 is connected between ground andconductor 368, its armatures being connected to conductors 349, 358,respectively. Th windings of relays 311, 318 are connected betweenbattery and conductors 386. 388, respectively. Conductor 383 terminatesat the No. 3 contact of bank 328?); conductor 381 terminates at the No.1 contact of bank 3260. Conductor 361 is connected to the off-normalcontacts of bank 328a.

Other connections plainly appear on the drawing and will appear from thesubsequent descrip-

